Milling tool



Oct. 17, 1944. I F, KlNzBACH 2,360,425

MILLING TOOL Filed oct. 11, 1941 31u/nervio@ Patented Oct. 17, 1944 UNITED STATES PATENT OFFICE MILLING TOOL vFrank Kinzbach, Houston, Tex. Application October 11, 1941,-SerialNo. 414,577 l (o1. 29-103) 2 Claims.

This invention relates to a milling tool.

An object of the invention is to provide a tool of the character described specially designed for milling a window in the side of a well casing so as to permit operations to be carried on through said window.

In drilling wells a casing is usually set in the well as the bore is deepened. It sometimes happens that an obstruction is encountered, as for example, when a pipe, drill, or the like, is inadvertently dropped into the well; or the bore may become deflected and it may become desirable to straighten the same. In either of the above events it is necessary to mill a window through the side of the well casing above the obstruction or at the point of deflection so that subsequent drilling operations can be carried on through the window and the well drilled deeper.

In the formation of this casing window, a deilector, commonly known as a whipstock, is set in the well casing at the point where it is desired to mill the window and a milling tool is then employed which is lowered into the casing on a drill stem and which is deflected by the whipstock against the side of the casing and upon rotation of the milling tool the window is gradually formed of a sufcient length to permit operations to be carried on through it. However, this casing is often formed of very hard material and offers considerable resistance to the milling tool causing the tool to cut away the whipstock rather than the casing itself.

It is the prime object of the present invention to provide a milling tool of the character described of such construction that the whipstock will be relieved, to a considerable extent at least, of the cutting action of the milling tool and the tool will be held firmly against the casing so that the major portionof the cutting action of the milling tool, while it is being rotated, will be against the casing rather than against the whipstock.

It is another object of the invention to provide a special type of milling tool for the above mentioned purpose having an elongated side boss arranged to bear against the deflector, or whipstock, and to hold the cutters of the milling tool firmly against the work while the boss is in contact with the whipstock, and which will be projected through the window, when the boss is in registration with the window, so as to relieve the cutting teeth of the milling tool from the deecting surface of the whipstock.

With the above and other objects in view the invention has particular relation to certain novel features of construction, arrangement of parts and use, examples of which are given in this specification and illustrated in the accompanying drawing, wherein:

Figure l shows a top plan view of the milling tool.

Figure 2 shows a side view thereof, partly in section.

Figure 3 shows an elevational view of another embodiment.

Figure 4 shows a lower end View thereof.

Figure 5 shows a horizontal, cross-sectional View taken through the casing window showing the boss in contact with the whipstock.

Figure 6 shows a similar View to that shown in Figure 5 showing the boss projecting through the casing window, and

Figure 7 shows a vertical, sectional view of a well casing with the whipstock therein, shown partly in section, and the milling tool in operation.

Referring now more particularly to the drawing wherein like numerals of reference designate the same parts in each of the gures the numeral I designates the body of the milling tool which is substantially cylindrical in form but whose forward end la may be tapered downwardly. The milling tool body is formed with an internally threaded box 2 to receive the pin of a drill co1- lar 3 carried by the drill stem and whereby the tool may be attached to said stem as shown in Figure '7. The cylindrical portion of the body I has the external cutters 5 thereon. These cutters are preferably inserted into the periphery of the body, in parallel arrangement and extending diagonally. The tapered portion 2 of the milling tool body is also provided with the cutters 6 preferably inserted therein and extending approximately radially with respect to the axis of the tool. However, the tool may be provided with any selected type of external cutters. In the type of tool shown in Figures 1 and 2 the body l is provided with an external, vertically elongated boss 1. This boss extends out radially slightly further than the cutters 5. As the milling tool is rotated when the boss comes into contact with the deflecting face 8 of the whipstock 9, the adjacent cutters on each side will be held out of contact with the whipstock as shown in Figure 5 and the 'opposing cutters will be held firmly against the material of the casing opposite the whipstock thus causing the casing to be cut away and the whipstock to be shielded or protected. When the boss reaches the window of the casing, it will project out through said window as shown in Figure 6 so that the opposing cutters will be relieved from the whipstock and will not mill the same away. The boss therefore while it reduces the total cutting action of the milling tool it will concentrate the effective cutting action against the casing and relieve it from the whipstock. This is very desirable where hard casing is encountered as otherwise the major portion of the cutting action of the tool would be exerted against the whipstock rather than against the side wall of the casing.

It will be observed from an inspection of Figure 7 that as the window is lengthened downwardly the milling tool will be deflected further and further toward the window side of the casing and eventually the cutters -6 of the lower or tapered end of the tool will take up the work of milling out the lower end of the window. When this point is reached the milling tool previously used, such as shown in Figure 2, should be withdrawn and the form shown in Figure 3 should be substituted for it and lowered into the Well and the milling operation resumed, This type of milling tool shown in Figure 3 has an elongated boss 'la arranged on the side of the tapering portion la of the body I. This boss 'la extends out radially slightly beyond the cutters 6 and as the work of carrying on the completion of the window proceeds, the boss 'la will alternately bear against the whipstock, and be projected out through the window as hereinabove described. While it is in contact with the deflecting face of the Whipstock the cutters 6 on each side will be held clear of the whipstock and will not cut it away and when the boss la projects through the window the opposing cutters of the tool will be relieved from the deflecting face of the whipstock and will not cut it away.

The above types of milling tool are especially useful where very hard casing is encountered which would resist the cutting action of the milling tool and cause it to cut into and destroy the whipstock rather than to mill out a window in the casing.

The drawing and description are illustrative merely while the broad principle of the invention will be defined by the appended claims.

What I claim is:

1. A milling tool comprising a body approximately cylindrical in shape and whose forward face is tapered to a frusto-conical shape, external cutting means carried by the body and arranged around said body and face and a lateral, integral, projection on the tapered portion of the body extending out therefrom beyond the cutting means on said tapered portion and terminating in a bearing face.

2. A milling tool comprising a body approximately cylindrical in shape and whose forward face is tapered to a frusto-conical shape, external cutting means carried by the body and arranged around said body and face, a lateral, integral, projection on the cylindrical portion oi the body and a lateral, integral, projection on the tapered portion of the body, said projections extending out from the cylindrical portion and the tapered portion beyond the corresponding cutting means thereof, each projection terminating in a bearing face.

FRANK KINZBACH. 

